Harvey Two-Face Dent is a fictional supervillain appearing in American comic books published by DC Comics, commonly as an adversary of the superhero Batman. The character was created by Bob Kane and Bill Finger, and first appeared in Detective Comics #66 (Aug. 1942).
reactivity. 1  the quality or condition of being reactive. 2  Chemistry. the relative capacity of an atom, molecule, or radical to undergo a chemical reaction with another atom, molecule, or compound. 3  Physics. a measure of the deviation from the condition at which a nuclear reactor is critical.
A chemical change must happen to be reactive. This reactivity can be fast or slow, toxic or nontoxic, explosive or calm. A periodic table can be used to help predict reactivity of an element. Examples of chemical reactivity include mixing substances to make a medicine and the mixture of a toxic spill with substances in the effected environment.